Only　rarely　have　polyoxometalates　been　found　to　form　core–shell　nanoclusters.　Here,　we　succeeded　in　isolating　a　series　of　rare　giant　and　all-inorganic　core–shell　cobalt　polyoxoniobates　(Co−PONbs)　with　diverse　shapes,　nuclearities　and　original　topologies,　including　50-nuclearity　{Co12Nb38O132},　54-nuclearity　{Co20Nb34O128},　62-nuclearity　{Co26Nb36O140}　and　87-nuclearity　{Co33Nb54O188}.　They　are　the　largest　Co−PONbs　and　also　the　polyoxometalates　containing　the　greatest　number　of　Co　ions　and　the　largest　cobalt　clusters　known　thus　far.　These　molecular　Co−PONbs　have　intriguing　and　atomically　precise　core–shell　architectures　comprising　unique　cobalt　oxide　cores　and　niobate　oxide　shells.　In　particular,　the　encapsulated　cobalt　oxide　cores　with　different　nuclearities　have　identical　compositions,　structures　and　mixed-valence　Co3+/Co2+　states　as　the　different　sized　Co−O　moieties　of　the　bulk　cubic-spinel　Co3O4,　suggesting　that　they　can　serve　as　various　molecular　models　of　the　cubic-spinel　Co3O4.　The　successful　construction　of　the　series　of　the　Co−PONbs　reveals　a　feasible　and　versatile　synthetic　method　for　making　rare　core–shell　heterometallic　PONbs.　Further,　these　new-type　core–shell　bimetal　species　are　promising　cluster　molecular　catalysts　for　visible-light-driven　CO2　reduction.　©　2023　Wiley-VCH　GmbH.